There are various reasons why network operators desire to measure traffic in their networks. Network measurement, for example, provides the data required for better network control, enabling the operator to characterize the state of the network, the traffic demands, and the actual consumption of network resources. Network measurement also enables trouble shooting or even prevents service-level agreement (SLA) violations before they occur.
With recent technological advancements such as Software-Defined Networking (SDN) and Network Function Virtualization (NFV), operators have coined the term “service chaining” to mean the differentiated forwarding of traffic flows across a policy defined ordered set of middle boxes (also commonly referred to as services, inline services, appliances, network functions/vNFs in case of NFV, or Service Functions (SF)). Examples SFs include firewalls, content filters, Intrusion Detection Systems (IDS), Deep Packet Inspection (DPI), Network Address Translation (NAT), content caches, load-balancers, Wide Area Network (WAN) accelerators, multimedia transcoders, logging/metering/charging/advanced charging applications, etc
Service chaining requires a classification process to forward packets on the correct service chain, followed by the differentiated forwarding/routing of the traffic flow across the right set of SFs or service function chain (SFC). Given the importance of this networking use case, the Internet Engineering Task Force (IETF) is developing protocols that will allow more efficient ways to implement SFCs. The IETF is also working on the definition of a Network Service Header (NSH) that will be applied to packets by the classifier. Then Service Function Forwarders (SFFs) will create the Service Function Paths (SFP) in the form of an overlay. IETF's solution is applicable to both physical Network Functions (NF) and virtual NFs (vNF) as defined by ETSI Network Functions Virtualization (NFV), referred to as SF in IETF.
In a typical service chaining system, probes (e.g., counters) can be instantiated (i.e., allocated) at various points in a SFP to perform network measurements. Existing network monitoring tools are not flexible and cannot perform consolidation of probes based on monitoring requests and rule consolidation. Moreover, none of the conventional network monitoring tools are specifically implemented around service function chaining, where existing forwarding plane rules and attached counters can be leveraged.